TVR S1 missfiring
Discussion
My S1 2.8 has got a missfire which is noticed most under hard acceleration, it runs fine on tickover and reving up when not moving but as soon as i go up the road it is there.
I have fitted new plugs, leads, distributer cap and tried a second hand coil but so far nothing has made a difference.
I have begun to wonder if it is fuel stavation and have fitted a new fuel filter but this also made no difference.
PLEASE HELP
I have fitted new plugs, leads, distributer cap and tried a second hand coil but so far nothing has made a difference.
I have begun to wonder if it is fuel stavation and have fitted a new fuel filter but this also made no difference.
PLEASE HELP
The only time I had a real misfire problem, I traced it to the ballast resistor that had corroded connectors. Cleaned them up and all was fine.
Dont forget to check the supply all the back via the tacho and fuse too just in case.
Edit to add the full diagnostic routine:
Engine turns but won't start
1)No fuel pressure;
Test the fuel pump and pre-pump and do a fuel pressure and volume test.
2)Jammed and/or sticking airflow sensor;
Remove the boot that goes to the intake and loosen the center line on fuel distributor.This will relieve
the control pressure.Press down on the center bolt of
the plate and you should feel no resistance or binding.Also check that the rest height and centering are correct.
3)Auxillary valve is sticking;
4)Defective cold start injector;
If the injector does not function,the air-fuel ratio will be lean,preventing easy start up.
5)Shorted or defective thermo time switch;
The cold start injector will not work if the thermo
time switch is defective.Check this in the event that your cold start injector does not function before replacing.
6)Control plunger sticking;
Remove the fuel distributor from the airflow sensor and check to see if it moves freely.
7)Restricted injectors;
For this to be the cause,they would have to be severely restricted,which is why I listed it last.Do
an injector flow test and ensure that the delivery is
near equal.
Hot starting difficulty
1)Loss of rest pressure;
Do a pressure test and focus on the rest pressure.If
it does not pass,check for a defective fuel pump check
valve,defective fuel distributor,faulty system pressure regulator and leaking cold start injector.
2)Airflow sensor adjusted incorrectly;
Check height,centering and for binding.Remove the boot and loosen the center line on fuel distributor to
relieve control pressure.
3)Sticking or binding of the control plunger;
Remove the fuel distributor and ensure that the control plunger moves freely.
4)Injectors leaking;
Remove the injectors from the intake manifold and with the ignition key on/engine off,press on the center plate to pressurize the system.Inspect and replace any injector that is leaking.
5)Cold start injector leaking;
Same test as above.
6)Shorted thermo time switch;
Cold start injector is dependent of this component.
7)Incorrect control pressure;
Do a pressure test and verify that the warm control pressure is within spec.
Rough idle (cold)
1)Cold control pressure incorrect;
The movement of the control plunger will be limited if the cold control pressure is too high.This in turn will limit the amount of fuel able to be delivered through the injectors.The result will be a lean ratio and will cause rough idle.
2)Auxillary air valve defective;
If defective and not opening,idle cannot rise and results in rough idle.
3)Airflow sensor adjusted improperly or binding;
If the movement is not smooth,it will result in air-fuel ratio errors.
4)Leaking cold start injector;
If the cold start injector is leaking,the engine will be overfueled even if cold.If the cold start injector is leaking,the idle will get worse as the engine temperature increases.
5)Injectors have an unequal flow or spray pattern;
Do an injector flow test and replace any that do not deliver the correct amount of fuel or have a poor spray pattern.
Runs rough (warm)
1)Warm control pressure incorrect;
Incorrect warm control pressure that is too high or low will cause an incorrect air-fuel ratio,thus resulting in a rough idle.
2)Airflow sensor adjusted improperly or binding;
If the movement is not smooth,it will result in air-fuel ratio errors.Check for centering and correct rest height.
3)Leaking cold start valve;
Again,will result in overfueling the engine,resulting in a rough idle.
4)Injectors have an unequal flow or spray pattern;
Do an injector flow test and replace any that do not
deliver the correct amount of fuel or have a poor spray pattern.
Stalls after starting (warm)
1)Warm control pressure;
If the warm control pressure is too high,the air-fuel
ratio will be lean.
2)System pressure incorrect;
If too high or low,the air-fuel ratio will be incorrect.
Idle speed high
1)Check auxillary air valve;
Ensure that it is closing.
2)Vacumm leaks;
Self explainatory.
3)Check the minimum air;
Self explainatory.
Backfire in intake
1)Check that CO adjustment is correct;
If incorrect,backfire will result if started and under a load.
2)Boot between airflow sensor and throttle defective;
Will result in a lean mixture due to secondary air(false air)
3)Vacumm leaks;
Self explainatory.
[b]Misfires
1)Ignition;
Inspect the cap,rotors,wires and plugs.
2)Fuel delivery inadequate;
Check for binding of airflow sensor,control plunger,
incorrect control or system pressure and restricted injectors.
3)Injectors;
Unequal delivery or poor spray pattern.Do a test and
replace any that are defective.[/b]
Poor power
1)Control pressure too high;
If the control pressure is too high,the control plungers travel will be limited,resulting in a lean running engine.
2)Check ignition components;
Verify that the spark plugs,wires,cap and rotor are not worn.
3)Injectors restricted;
Do a test for delivery.If an injector is restricted,fuel delivery will be limited,thus power will suffer.
Sag or stumble when accelerating
1)Airflow sensor plate binding or sticking;
If binding or sticking,fuel flow will be limited.
2)Control plunger binding or sticking;
If binding or sticking,fuel flow will be limited.
3)System pressure or warm control pressure incorrect;
If too high,the travel of the plunger will be limited.
4)Injector flow unequal;
Self explainatory.
Diesels(run on after shut off)
1)Airflow sensor sticking or binding;
The plate is not rising to position,continuing to deliver fuel.
2)Control plunger binding or sticking;
Remove the fuel distributor and ensure that the control plunger moves freely.
3)Injectors leaking;
Do an injector flow test and make sure that they seat correctly.Replace any that are defective.
4)Cold start injector leaking;
Remove and pressurize the system and replace if it leaks.
Fuel consumption high
1)Air-fuel ratio incorrect
2)Injectors leaking
3)Cold start injector leaking
Dont forget to check the supply all the back via the tacho and fuse too just in case.
Edit to add the full diagnostic routine:
Engine turns but won't start
1)No fuel pressure;
Test the fuel pump and pre-pump and do a fuel pressure and volume test.
2)Jammed and/or sticking airflow sensor;
Remove the boot that goes to the intake and loosen the center line on fuel distributor.This will relieve
the control pressure.Press down on the center bolt of
the plate and you should feel no resistance or binding.Also check that the rest height and centering are correct.
3)Auxillary valve is sticking;
4)Defective cold start injector;
If the injector does not function,the air-fuel ratio will be lean,preventing easy start up.
5)Shorted or defective thermo time switch;
The cold start injector will not work if the thermo
time switch is defective.Check this in the event that your cold start injector does not function before replacing.
6)Control plunger sticking;
Remove the fuel distributor from the airflow sensor and check to see if it moves freely.
7)Restricted injectors;
For this to be the cause,they would have to be severely restricted,which is why I listed it last.Do
an injector flow test and ensure that the delivery is
near equal.
Hot starting difficulty
1)Loss of rest pressure;
Do a pressure test and focus on the rest pressure.If
it does not pass,check for a defective fuel pump check
valve,defective fuel distributor,faulty system pressure regulator and leaking cold start injector.
2)Airflow sensor adjusted incorrectly;
Check height,centering and for binding.Remove the boot and loosen the center line on fuel distributor to
relieve control pressure.
3)Sticking or binding of the control plunger;
Remove the fuel distributor and ensure that the control plunger moves freely.
4)Injectors leaking;
Remove the injectors from the intake manifold and with the ignition key on/engine off,press on the center plate to pressurize the system.Inspect and replace any injector that is leaking.
5)Cold start injector leaking;
Same test as above.
6)Shorted thermo time switch;
Cold start injector is dependent of this component.
7)Incorrect control pressure;
Do a pressure test and verify that the warm control pressure is within spec.
Rough idle (cold)
1)Cold control pressure incorrect;
The movement of the control plunger will be limited if the cold control pressure is too high.This in turn will limit the amount of fuel able to be delivered through the injectors.The result will be a lean ratio and will cause rough idle.
2)Auxillary air valve defective;
If defective and not opening,idle cannot rise and results in rough idle.
3)Airflow sensor adjusted improperly or binding;
If the movement is not smooth,it will result in air-fuel ratio errors.
4)Leaking cold start injector;
If the cold start injector is leaking,the engine will be overfueled even if cold.If the cold start injector is leaking,the idle will get worse as the engine temperature increases.
5)Injectors have an unequal flow or spray pattern;
Do an injector flow test and replace any that do not deliver the correct amount of fuel or have a poor spray pattern.
Runs rough (warm)
1)Warm control pressure incorrect;
Incorrect warm control pressure that is too high or low will cause an incorrect air-fuel ratio,thus resulting in a rough idle.
2)Airflow sensor adjusted improperly or binding;
If the movement is not smooth,it will result in air-fuel ratio errors.Check for centering and correct rest height.
3)Leaking cold start valve;
Again,will result in overfueling the engine,resulting in a rough idle.
4)Injectors have an unequal flow or spray pattern;
Do an injector flow test and replace any that do not
deliver the correct amount of fuel or have a poor spray pattern.
Stalls after starting (warm)
1)Warm control pressure;
If the warm control pressure is too high,the air-fuel
ratio will be lean.
2)System pressure incorrect;
If too high or low,the air-fuel ratio will be incorrect.
Idle speed high
1)Check auxillary air valve;
Ensure that it is closing.
2)Vacumm leaks;
Self explainatory.
3)Check the minimum air;
Self explainatory.
Backfire in intake
1)Check that CO adjustment is correct;
If incorrect,backfire will result if started and under a load.
2)Boot between airflow sensor and throttle defective;
Will result in a lean mixture due to secondary air(false air)
3)Vacumm leaks;
Self explainatory.
[b]Misfires
1)Ignition;
Inspect the cap,rotors,wires and plugs.
2)Fuel delivery inadequate;
Check for binding of airflow sensor,control plunger,
incorrect control or system pressure and restricted injectors.
3)Injectors;
Unequal delivery or poor spray pattern.Do a test and
replace any that are defective.[/b]
Poor power
1)Control pressure too high;
If the control pressure is too high,the control plungers travel will be limited,resulting in a lean running engine.
2)Check ignition components;
Verify that the spark plugs,wires,cap and rotor are not worn.
3)Injectors restricted;
Do a test for delivery.If an injector is restricted,fuel delivery will be limited,thus power will suffer.
Sag or stumble when accelerating
1)Airflow sensor plate binding or sticking;
If binding or sticking,fuel flow will be limited.
2)Control plunger binding or sticking;
If binding or sticking,fuel flow will be limited.
3)System pressure or warm control pressure incorrect;
If too high,the travel of the plunger will be limited.
4)Injector flow unequal;
Self explainatory.
Diesels(run on after shut off)
1)Airflow sensor sticking or binding;
The plate is not rising to position,continuing to deliver fuel.
2)Control plunger binding or sticking;
Remove the fuel distributor and ensure that the control plunger moves freely.
3)Injectors leaking;
Do an injector flow test and make sure that they seat correctly.Replace any that are defective.
4)Cold start injector leaking;
Remove and pressurize the system and replace if it leaks.
Fuel consumption high
1)Air-fuel ratio incorrect
2)Injectors leaking
3)Cold start injector leaking
Edited by Le TVR on Thursday 16th July 08:20
I had a similar thing on my S2 recently. After changing all the ignition system parts, I eventually traced it to an air leak on the inlet hose after the air flow meter. Not sure about the layout on the S1 but it's worth going over the whole induction system to check for leaks. Symptoms were almost exactly the same...revved up sweet as anything on the drive, severe misfire under any sort of load.
Cheers
Ant
Cheers
Ant
Hi Graham
Welcome to the forum
As Kev says I have had a couple of problems along those lines. One was fuel related;I found my tank was full of rust and clogging the pump and the other was a loose connector on the fuel pump relay.
On mine there is a small thimble like strainer at the inlet to the fuel pump ~ this was getting clogged with rust.
See here for my tales of woe http://tinyurl.com/mhhgv2
and the solution : http://tinyurl.com/l3gjpl
Picture of relay on this thread http://tinyurl.com/nu2l9k ( fault found by using diagnostic tool) http://tinyurl.com/kqmhkx
Mine is an S2 not an S1 ~ I'm not sure how relevant all these issues are to you, but it is a good place to start.
Cheers
Tim
Welcome to the forum
As Kev says I have had a couple of problems along those lines. One was fuel related;I found my tank was full of rust and clogging the pump and the other was a loose connector on the fuel pump relay.
On mine there is a small thimble like strainer at the inlet to the fuel pump ~ this was getting clogged with rust.
See here for my tales of woe http://tinyurl.com/mhhgv2
and the solution : http://tinyurl.com/l3gjpl
Picture of relay on this thread http://tinyurl.com/nu2l9k ( fault found by using diagnostic tool) http://tinyurl.com/kqmhkx
Mine is an S2 not an S1 ~ I'm not sure how relevant all these issues are to you, but it is a good place to start.
Cheers
Tim
Hi Graham. I had a similar problem on my S1 - if you really gunned it it would suddenly stall briefly. It was ok pootling along but any enthusiastic driving resulted in spluttering. I heard the fuel pump cough a bit at some lights, so I changed that to a oem one off ebay for a ford orion and it totally sorted it. It was a different car after that - much keener accelerating!
HTH
Jim
HTH
Jim
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